Pouring nozzle

ABSTRACT

The invention relates to a pouring nozzle. Such pouring nozzle may be used for the transfer of a metal melt from one (upper) metallurgical vessel to a second (lower) metallurgical vessel, for example for the transfer of a steel melt from a ladle to a tundish.

The invention relates to a pouring nozzle. Such pouring nozzle may beused for the transfer of a metal melt from one (upper) metallurgicalvessel to a second (lower) metallurgical vessel, for example for thetransfer of a steel melt from a ladle to a tundish.

Such pouring nozzles are made of at least one refractory material (towithstand the high melt temperatures) and comprise a tubular region,defining a first part of a pouring channel, and a plate like region withan orifice defining a second part of said (common) pouring channel. Saidplate like region which usually is integral with said tubular region isarranged at one end of the tubular member. This leads to a T-like designof the total pouring nozzle.

Typically two of said pouring nozzles are arranged in the outflow areaof a metallurgical melting vessel. One of said two nozzles being mostlyarranged within the refractory lining of the vessel, e.g. within a wellblock. This so called inner nozzle is mounted with its tubular region atits upper end and the plate like region at its lower end.

By this installment the plate like region may be used as one part of asliding gate valve. For this purpose the plate like region has a flatsurface at its free (lower) end, which flat surface runningperpendicular to a longitudinal axis of the pouring channel, i.e. moreor less horizontal in the mounted position of the pouring nozzle.

Correspondingly a second nozzle (often called outer nozzle or exchangenozzle) may be installed below said inner nozzle, e.g. mounted viceversa with its plate like part at its upper end and the tubular part atits lower end. This nozzle often may be moved after installation. Againthe free surface of the plate like region should be flat so as it may beused as a sliding surface within a 2 or 3 plates sliding mechanism.

It is further known to encapsulate a least part of such a nozzle by ametallic envelope (metal casing). This casing stabilizes the nozzle andfacilitates the exchange of the nozzle. The metallic can furtherprovides the necessary geometrical accuracy for effective fit with acorresponding operational or exchange mechanism and mechanical supportto the relatively brittle refractory ceramic nozzle components.

Due to a combination of thermo-mechanical forces established duringpreheat of the nozzle, exchange motion and/or cast operation stressesare created within the nozzle which may result in cracks through itswall, especially at the transition area where the plate and tubularportions meet.

The inventors have analyzed by computer simulation studies the originsof said crack formation. It was noted that for the lower (moving)element the highest stresses occur over the support mechanism for saidnozzle and being greatest at the central transverse axis over theloading mechanism. In the classical “T” form of a pouring nozzle thesesupport forces create a highly stressed zone between the support surfaceand the pouring channel along which a crack may propagate from theexterior to the bore (pouring channel) of the tube section under thesupport flange (the plate like member).

It was further observed that under operating conditions differentialexpansion causes surface deflection. Whilst the surfaces of the pair ofplates around the pouring channel remain in intimate contact with eachother plate surfaces in the outer areas become separated as illustratedin FIG. 1.

It is an object of the invention to provide a pouring nozzle which mayeither be used as inner or outer nozzle which provides the necessaryaccuracy for effective fit within a corresponding holding or pushingmechanism while at the same time providing the necessary stability overthe range of the temperatures encountered in assembly, preheat andoperation.

It has been found by the inventors that the disadvantages of prior artdevices may be overcome by the arrangement of at least one stiffeningelement within the refractory material of the plate like member orbetween said plate like member and the metallic envelope. A furtheralternative, which leads to similar results, is to make the stiffeningelement part of the metallic envelope such that the stiffening elementthen protrudes into the refractory material of said plate like member.

In its most general embodiment the invention relates to a pouring nozzlemade of at least one refractory material and comprising a tubular memberdefining a first part of a pouring channel and a plate like memberintegral with said tubular member and projecting from the tubular memberalong its periphery at the one end, said plate like member having anorifice defining a second part of said pouring channel and a flatsurface at its free end, which flat surface running perpendicular to alongitudinal axis of said pouring channel, at least part of the platelike member and/or of the tubular member being encapsulated by ametallic envelope, wherein at least one stiffening element is arrangedwithin the refractory material of said plate like member, between saidplate like member and the metallic envelope or protruding from saidmetallic envelope into the said plate like member.

The design configuration of the external encapsulation facilitatesintroduction of integral stiffening within the support can. The extrarigidity provided by such integral, internal stiffening elementsintroduces the potential to absorb the point loading forces from acorresponding support mechanism and distribute any such forces evenlyacross a wide area of the encapsulated refractory ceramic material andthereby onto the head and tubular regions of the nozzle.

Various design configurations of the integral stiffening elements arepossible to provide maximum strength with minimum weight and maximumcompatibility with the support mechanism of the nozzle change device.

According to one embodiment the pouring nozzle comprises two stiffeningelements, arranged at opposite ends of said plate like member. Typicallythe plate like member is shaped as a parallelepiped, especially whenused within a sliding gate arrangement. It then comprises two (of four)opposite support flanges against which the support mechanism acts.

The stiffening elements may have various shapes. They can be shaped as arod, as a helical spring, as a bar or the like.

Along with pouring nozzles comprising a plate like member with acircular free surface area the plate like member may have the shape of aring.

The stiffening element (reinforcement element) may be fully surroundedby refractory ceramic material (first alternative). It may also bearranged between the refractory ceramic material and the metallicenvelope (alternative 2). In alternative 3 the reinforcement member ispart of the metallic envelope and arranged like a flange along the innerwall of said envelope. All these three embodiments will be furtherdisclosed by examples hereinafter.

The stiffening element may be arranged such that one of its surfacesforms part of the flat surface of the plate like member. It is thenpreferably arranged at the outer periphery of the flat surface of theplate like member. This minimizes the risk of any deflection in theouter peripheral region of the plate like member according to FIG. 1.

As principally disclosed in EP 1 133 373 B1 a shock absorbing interfacezone may be arranged between the basic (inner) refractory material andthe stiffening element(s) and/or the (outer) metallic envelope. Saidshock absorbing interface zone may be made of a second refractorymaterial which becomes deformable at temperatures experienced during useof said pouring nozzle in metal casting. For further details referenceis made to EP 1 133 373 B1.

The inventive concept may be applied to pouring nozzles of a strongT-shape, i.e. nozzles comprising a plate like region the supportingsurfaces of which running more or less parallel to the flat surface attheir free end. The concept may as well be applied to nozzles accordingto FIG. 3 of EP 1 133 373 B1 (identical to nozzles according to EP 1 590114 B1) comprising bearing surfaces (opposite the free flat surface)which bearing surfaces form an angle unequal 90° with the longitudinalaxis of the pouring channel.

In the latter case part(s) of the stiffening element(s) form part of thechamfered surface sections (bearing surfaces).

The stiffening element(s) may be made of any material improving themanufacturing, use or exchange of a pouring nozzle for metal casting.One of the most favorite materials is metal but a ceramic of highmodulus of rupture may be favorite as well.

Further features of the invention are disclosed in the sub claims andthe other application documents.

The invention will now be described in more detail relating to theattached drawing, which schematically shows:

FIG. 1: A cross sectional view of a pouring nozzle according to priorart after use.

FIG. 2: A cross sectional view of a pouring nozzle according to theinvention (embodiment 2).

FIG. 3: A cross sectional view of a pouring nozzle according to theinvention (embodiment 3).

FIG. 4: A cross sectional view of a pouring nozzle according to theinvention (embodiment 1).

FIG. 1 shows an inner nozzle 10 and an outer nozzle 12 of a generallyT-shaped design with flanges of similar geometric design but bothnozzles 10, 12 could as well be characterised by identical designs.

During use under operating conditions at elevated temperaturesdifferential expansion causes surface deflection within said knownnozzle. A contact between the respective flat surface sections 10 s/12 sis only maintained around a central pouring channel 14 while outersurface areas 12 so separate and create unrestrained regions free todeflect under the pressure of closing forces (arrows C) creating abending/tearing stress concentrated at the meeting point of the platelike part and the tubular element which may cause a crack “CS” from theexterior towards bore 14.

Nozzle 12 of FIG. 2 comprises a tubular region 12 t defining a firstpart of pouring channel 14. Said tubular part 12 t is made from a commonrefractory ceramic material and is integral with a plate like region 12p following upwardly. Said plate like region 12 p is of larger crosssectional area than part 12 t and comprises an inner part 12 pi made ofthe same refractory material as tubular member 12 t and two metallicparts 12 pm running alongside two opposite sides of the inner part 12pi. While the inner surfaces of the metallic parts 12 pm are touchingthe corresponding outer surface areas of the refractory part 12 pi theouter surfaces of part 12 m are in contact with an envelope 16, asdescribed hereinafter.

Said plate like member 12 p provides a flat upper surface 12 s at itsfree end (opposite tubular part 12 t) which surface 12 s being definedby a combination of corresponding surfaces of the refractory part 12 piand said two metallic reinforcement inserts 12 pm, representingstiffening elements. Following the outer (peripheral) design the saidstiffening elements (metallic parts 12 pm) are characterised by an uppervertical outer surface 12 pmo, followed by an inclined surface portion12 pmi while the respective inner walls are running vertical from uppersurface 12 s to the respective lower ends.

A metallic can 16 encapsulates the plate like member 12 p and theannexed area of tubular member 12 t. The longitudinal axis of thisnozzle 12 is marked as “L”.

When nozzle 12 of FIG. 1 is replaced by one incorporating the designshown in FIG. 2 with the integral stiffening members, the temperatureconditions arising from service again generate a differential thermaldeflection across the plate surface 12 s. However the said stiffeningelements 12 pm bear the pressures from the closing mechanism and preventthem from establishing any bending stress moment across the refractorymaterial of the nozzle 12.

Besides this important effect nozzle 12 according to FIG. 2 provides thefurther advantage that its chamfered bearing surfaces, provided by thecan sections opposite surface sections 12 pmi present increasedmechanical stability because the stiffening elements 12 pm are arrangeddirectly behind this bearing surfaces.

A similar effect may be achieved by a pouring nozzle 12 according toFIG. 4 which differs from that of FIG. 2 just in the arrangement of saidtwo stiffening elements 12 pm.

Both stiffening elements 12 pm are designed as rods (bars) and placedwithin the refractory ceramic material of plate like member 12 p, i.e.they are fully surrounded by said refractory material.

The respective cross sectional area is adapted to the outer design ofplate like member 12 p. Especially said stiffening element 12 pmprovides inclined lower surface sections 12 pmi running parallel tocorresponding inclined bearing surfaces 16 b of metal can 16.

FIG. 3 represents a pouring nozzle 10 used as an inner nozzle accordingto inner nozzle 10 of FIG. 1.

Nozzle 10 again comprises a tubular part 10 t followed (here: at itslower end) by a plate like part 10 p. The transition area betweentubular part 10 t and plate like part 10 p is marked as “T”.

FIG. 3 shows that tubular part 10 t is—at its lower end—surrounded by asleeve 18, made of a refractory material different to that of part 10 t.This sleeve 18 continues around the plate like member 10 p and in turnis encapsulated by an outer metallic envelope 16 which ends shortlybefore the free and flat surface area 10 s at the lower end of nozzle10.

A shock absorbing interface layer “S”, made from a material whichbecomes deformable at the temperatures experienced during use of saidpouring nozzle, may be introduced between the refractory pouring nozzleelement 10 p and the second surrounding refractory sleeve 18.

Following the shape of sleeve 18 can 16 is characterised by acylindrical part at its upper end, followed by an inclined (outwardlyextending) portion 16 b and an outwardly extending horizontal part 16 hfollowed by a final vertically running portion 16 v.

That part of envelope 16 provided by horizontal part 16 h and verticalportion 16 v is mechanically reinforced by two stiffening elements 10pm, protruding from opposing inner wall of envelope 16. Both of saidstiffening elements are designed as rods with a rectangular squaresection. They are replacing part of encapsulating material of sleeve 18.

The refractory material of tubular part 10 t extends into the area ofplate like member 10 p and is characterised by an outwardly taperedportion 10 pi providing the inner part of surface section 10 s aroundthe pouring channel 14.

The two metal bars 10 pm again act as stiffening elements similar tostiffening elements in FIGS. 2 and 4. According to the embodiment ofFIG. 3 theses stiffening elements 10 pm are integral part of the outermetallic envelope 16.

The shape of the can and any adjacent stiffening means like 12 pm or 10pm in any of the embodiments shown may have a profile suited to anyspecific mechanism configuration.

1. Pouring nozzle made of at least one refractory material andcomprising a tubular member (10 t, 12 t) defining a first part of apouring channel (14) and a plate like member (10 p, 12 p), integral withsaid tubular member (10 t, 12 t) and projecting from the tubular member(10 t, 12 t) along its periphery at one end, said plate like member (10p, 12 p) having an orifice defining a second part of said pouringchannel (14) and a flat surface (10 s, 12 s) at its free end, which flatsurface (10 s, 12 s) running perpendicular to a longitudinal axis (L) ofsaid pouring channel (14), at least part of the plate like member (10 p,12 p) and/or of the tubular member (10 t, 12 t) being encapsulated by ametallic envelope (16), wherein at least one stiffening element (10 pm,12 pm) is arranged within the refractory material of said plate likemember (10 pm, 12 p), between said plate like member (10 p, 12 p) andthe metallic envelope (16) or protruding from said metallic envelope(16) into the said plate like member (10 p, 12 p).
 2. Pouring nozzleaccording to claim 1, comprising two stiffening elements (10 pm, 12 pm),arranged at opposite sides of said plate like member (10 p, 12 p). 3.Pouring nozzle according to claim 1, wherein the stiffening element hasthe shape of a rod.
 4. Pouring nozzle according to claim 1, wherein thestiffening element has the shape of a helical spring.
 5. Pouring nozzleaccording to claim 1, wherein the stiffening element has the shape of aring.
 6. Pouring nozzle according to claim 1, wherein the stiffeningelement (10 pm) is part of the envelope (16), which stiffening element(10 pm) protrudes from the inner wall of said envelope into saidrefractory material of said plate like member (10 p).
 7. Pouring nozzleaccording to claim 1, wherein the stiffening element (12 pm) is arrangedsuch that one of its surfaces forms part of the flat surface (12 s) ofthe plate like member (12 p).
 8. Pouring nozzle according to claim 7,wherein the stiffening element (12 pm) is arranged at the outerperiphery of the flat surface (12 s) of the plate like member (12 p). 9.Pouring nozzle according to claim 1, wherein chamfered surface sectionsof said plate like member opposite its flat surface form an angle αbetween 20 and 85° with the longitudinal axis (L) of the pouringchannel.
 10. Pouring nozzle according to claim 9, wherein part(s) of thestiffening element(s) form part of the said chamfered surface sections ().
 11. Pouring nozzle according to claim 1, comprising a secondrefractory zone (18) between the envelope (16), the stiffeningelement(s) (10 pm) and the plate like member (10 p).
 12. Pouring nozzleaccording to claim 11, where a shock absorbing interface zone (S) isarranged between zone (18) and plate like member (10 p) and made from arefractory material, which becomes deformable at temperaturesexperienced during use of said pouring nozzle.
 13. Pouring nozzleaccording to claim 1, comprising at least one metallic stiffeningelement (10 pm, 12 pm).
 14. Pouring nozzle according to claim 1,comprising at least one high density ceramic stiffening element (10 pm,12 pm).